Thanks for the info. After posting the message I did find FAR 23 and
extracted the info there for airplanes.

We have Mountain High Constant Flow systems installed in parallel with our
A-14s. I have been in conversation with MH.

I continue to have little luck in getting specific documents on servicing
the A-14s. I have struck out on getting service on them. Several outfits
that use to do it, no longer do it. I'm still waiting to hear from Fluid
Power of Ohio.

Bottom line is we can fly to 30,000' with our MH systems and appropriate
masks.

John Scott